A handful of Google engineers and designers are building a phone the DARPA way

The broad outlines of Project Ara have already been announced and had plenty of doubt cast on them. It's an attempt to encourage hardware manufacturers to build modules that will slot into a metal "endoskeleton," which serves as the basic core of a phone. The camera, screen, and any other feature that you'd traditionally associate with a smartphone would exist only as a modular tile — even the processor and the power jack would be removable.
The challenges that ATAP needs to overcome are formidable to say the least. Since well before the iPhone, mobile technology has been on an inexorable march towards integration. Putting as many parts as possible on a single circuit board — or even a single chip — has benefits that are impossible to ignore. Integration saves on battery life, weight, thinness, and cost, among other things.